Twin, or dual, scroll turbocharger configurations may be used in turbocharged engines. A twin scroll turbocharger configuration may separate an inlet to a turbine into two separate passages connected to exhaust manifold runners. In this way, exhaust from the engine cylinders, whose exhaust gas pulses may interfere with each other, are fluidically separated.
For example, on an I4engine with a cylinder firing order of exhaust manifold runners 1-3-4-2, exhaust manifold runners 1 and 4 may be connected to a first inlet of a twin scroll turbine and exhaust manifold runners 2 and 3 may be connected to a second inlet of said twin scroll turbine, where the second inlet is different and fluidically separated from the first inlet. In this way, separating exhaust gas pulses may result in an increase in efficiency of exhaust gas delivery to a turbine in some cases.
However, under some engine operating conditions, separating exhaust gas pulses as described above may reduce an efficiency of exhaust gas delivery to a turbine. For example, under certain engine operating conditions, e.g., high speed and high load conditions, separating exhaust gas pulses may result in an increase in backpressure and pumping work. This increase in backpressure and pumping work may be due to more restrictive, lower volume passages between the exhaust and the turbine in a dual scroll turbine, as compared to a passage that is not separated in a single scroll turbine. As such, the amount of exhaust gas in the cylinder may raise the pressure in the lower volume passages compared to the relatively larger volume, unseparated passage. The increased backpressure may also result in higher levels of residual gas having excessive temperatures in the cylinder, thereby reducing the engine's output power and engine efficiency.
One example approach for reducing backpressure and pumping work in a twin scroll turbocharger has been shown by Styles et al. in U.S. 2014/0219849. Herein, systems positioning a branch communication valve between a first scroll and a second scroll in a twin (e.g., dual) scroll turbocharger system are provided. In an example, a branch communication valve may be positioned in a passage within a wall separating a first scroll and a second scroll of the twin turbocharger. In an open position, the branch communication valve may increase fluid communication between the first and second scroll, and in a closed position, the branch communication valve may decrease fluid communication between the first and second scroll. The branch communication valve of Styles et al. comprises a valve plate rotatable about a hinge, the hinge positioned within a recess of the second scroll. The valve plate is movable between a first position, wherein the valve plate covers the opening in the dividing wall, and a second position, wherein the valve plate is within the recess.
The inventors herein have recognized a potential issue with the example approach of Styles et al. For example, there may be cost, weight, and packaging penalties associated with the above configuration of branch communication valve having a valve plate rotatable about a hinge in the turbocharger and engine system. For example, the hinge is shown in a recess of the second scroll, which increases the size and complexity of manufacturer of the turbocharger system. Further, the branch communication valve comprises a valve plate and valve stem, the valve plate slidable to cover the opening. As such, these components, such as the valve plate and valve stem, are exposed to high temperatures and, thus, may wear overtime. The components may also be an additional burden on an engine control and monitoring system when the aforementioned system is adjusted on engine operating conditions.
The inventors herein have identified an approach to at least partly address the above issue. In an example, a method for an engine is provided, comprising adjusting a position of a valve arranged between a first adaptor and a second adaptor to enable mixing of exhaust received from an exhaust manifold responsive to engine load and engine speed, the exhaust delivered to a first scroll and a second scroll of a turbocharger, wherein the first adaptor includes a first divider, the second adaptor includes a second divider, and the valve includes a third divider. In this way, there may be a reduction in flow restriction during certain engine operating conditions, such as high engine speed and/or high engine load.
In one example, the method may adjust a valve to provide one of a separation of exhaust and mixing of exhaust, wherein the valve varies a degree of mixing of exhaust received from an exhaust manifold. As such, each of the first adaptor and second adaptor may be stationary, while the valve may rotate about the central axis to selectively vary a degree of alignment of the third divider of the valve relative to the first divider of the first adaptor and the second divider of the second adaptor. In this way, the method may provide a straightforward and uncomplicated controls and systems for regulating pulsation flow to the turbocharger based on various engine operating conditions.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.